Boeing's Phantom Works is leading the effort to demonstrate the Massive Ordnance Penetrator (MOP). The three-phase technology demonstration builds on design studies that Boeing had conducted for the laboratory. Flight testing is envisaged around 2006. The 6 m [20 feet] long MOP features short-span wings and trellis-type tails. The 13,600 kg [30,000 lb] weapon contains a 2,700 kg [6,000 lb] explosive charge. MOP is designed to go deeper than any nuclear bunker buster and take out 25 percent of the underground and deeply buried targets. It is expected to penetrate as much as 60 meters [200 feet] through 5,000 psi reinforced concrete. It will burrow 8 meters into the ground through 10,000 psi reinforced concrete. Northrop Grumman is working on with Boeing to develop this conventional bunker buster. They are under contract to Air Force Research Laboratory's Munitions Directorate at Eglin Air Force Base, Florida, and Defense Threat Reduction Agency.

LE

The US has been working on 'conventional' deep-penetration weapons for years now, primarily to deal with the North Korea/Iran nuke programmes. The only alternative was just too much to contemplate, even for the Bush administration, but it appears that the conventional route may have worked, as efforts for deep-penetrating nukes have now (AFAIK) been terminated.

Ah a beautiful pic, one of those could and often did granulate an entire Berlin City block. Also it should be noted that when the US President annonced to the US public the dropping of the A Bomb he compared it as being bigger than the 'British Grandslam'. Which indicates that it was well known in the US.

'There is much to learn from the British: their reticence about disclosing details, their clear expertise in human intelligence, their non-hysterical reaction to very real threats. Many Americans may have an inferiority complex about things British -- the refinement, the style and, of course, those accents' -

Listy, you are correct - the Main Force Bombers would regularly drop 8000 lb "blockbusters" or "cookies" on their raids, along with incendaries. These were little more than dustbins full of TNT. The idea was that the cookies would open up houses and the incendaries would set fire to the wreckage. See Dresden/Hamburg/Cologne for when it worked.

The supply of Tallboys and Grand Slams was very carefully husbanded and used on special targets only.

ADC

'There is much to learn from the British: their reticence about disclosing details, their clear expertise in human intelligence, their non-hysterical reaction to very real threats. Many Americans may have an inferiority complex about things British -- the refinement, the style and, of course, those accents' -

Old-Salt

The Grand Slam is actually very relevant to the role envisaged for this MOP toy... One of its roles was to take out targets like bridges and tunnels by shaking them to bits as a result of delayed initiation after it had penetrated the ground (went supersonic on the way down, IIRC). I'd imagine that, if we could find a spare one tucked away somewhere, and drop it in the middle of an Afghan cave complex, it'd do quite a good job of making sure everyone inside never saw the light of day again. Meanwhile, some 'MOABs' above ground to deafen everyone within a few square miles, and bob's yer uncle..

I thought they where after the âTrapdoorâ effect, where the bomb Penetrates the ground and creates a huge cavern underneath the target, basically undermining it, it then collapses into the hole. Think of the footage you've seen of some of the underground nuke tests in Nevada. That sort of effect.

The really scary thing about the tallboy (and the Grandslam) was that it wasn't dropped from high enough altitude to achieve full effect, as Lancs couldn't get the altitude Barns Wallis envisaged.

You are right ,I read the 30,000 and went blank ,stunned . That does put it in a better perspective. In further checking, a 2000 pound bomb has 650 pounds of explosive. I have seen pictures of the crater a 2,000 pound bomb and they are immense. The explosion of 6000 pounds of explosive must be hard to imagine, but Nuclear weapons are in a category by themselves.

War Hero

Bear in mind also that modern explosives have a higher Figure of Power than the TNT in Grandslams and similar so their 'yield' will be greater. For effects of Grandslams have a look for details of the U Boat pens at Brest.

There may also be some wave guidance or other charge manipulation involved.

Old-Salt

Almost - but there have been blast/damage tests that get up to 'kiloton level': this page shows a half-kiloton blast at Suffield (Scroll down to 1960 - if you've seen the crater at the middle, you've seen it's location...) Basically a darn great pile of HE. Must be a laugh to set off...